The present invention relates to a motor vehicle, especially to a passenger motor vehicle in which for purposes of achieving road traction of the vehicle, the vehicle floor in the rear area is constructed essentially smooth-surfaced and rising toward the vehicle end and an air foil is arranged in the space underneath the rising rear floor, where a negative lift becomes effective with an incident flow coming from the vehicle front section.
In a known motor vehicle of this type which is constructed as passenger motor vehicle, the vehicle floor is bent upwardly shortly before its rear end and the air foil which in plan view has the shape of a section of a circle whose circular arc forms the front edge of the air foil, is arranged underneath the horizontal vehicle floor located in front of the bending place and of the rising rear floor in such a manner that it adjoins with its rear, upwardly directed end the inclined surface formed by the rising rear floor so that the inflowing air is conducted toward both vehicle sides (French Patent No. 1,529,933).
In another known passenger motor vehicle (U.S. Pat. No. 4,379,582, JP-GM-OS Sho No. 55-117369), a rear bumper unit is provided which includes a main bumper secured at the vehicle body and a further bumper which is arranged underneath the main bumper while leaving free an inclined rearwardly rising air opening, and which is secured at the main bumper. The further bumper as also its mountings consist of shock-absorbing elastic material, is constructed as air foil with inverted air foil profile and with its forward end protrudes over the forward area of the main bumper forwardly underneath the rear end of the rear section of the vehicle body.
A further passenger motor vehicle with an air foil having an air foil profile which is arranged underneath the rear area of the vehicle body and guides inflowing air coming from the front obliquely rearwardly, is disclosed in the JP-GM-OS Sho No. 52-63828.
The known air foils are always arranged only in the rear area. They act essentially as air guide devices.
The present invention is concerned in the first instance with the task to provide a motor vehicle of the aforementioned type which is suitable for the practical use in the usual road traffic and has an aerodynamic configuration which assures a good road traction, especially also at high driving velocities.
The underlying problems are solved according to the present invention in that the forward end of the rising rear floor is arranged at least approximately within the area of the vehicle rear axle, in that the rising rear floor forms the top side of a rear diffusor whose bottom side is formed by the road surface, and at the vehicle end has a considerable spacing from the vehicle-tire contact surface (road surface), and in that the air foil is so arranged that it protrudes with its forward end into the space between the vehicle rear wheels and its bottom side has at least the same distance from the vehicle tire contact surface as the vehicle floor at its lowest place in the vehicle areas located in front of the vehicle rear section. It is achieved thereby that a considerable negative lift dependent on driving velocity is produced at the vehicle rear section with simple means without a deviation of the external configuration of the vehicle from the usual configuration in a disturbing manner, which configuration is fixed far-reachingly by legal rules and regulations and by practical requirements. The present invention is advantageous in particular for smaller and more light-weight vehicles, especially for sporty two-seaters. It enables not only a good traction but also the production of high lateral guide forces and therewith a good tracking and driving stability. It can be used in vehicles with different types of drive, for example, in vehicles with a standard drive, i.e., with a forwardly arranged engine and a rear wheel drive, in vehicles with front engine and front wheel drive or in those with four wheel drive.